The methacholine challenge test was first approved by the FDA in 1986 and since then has been included in various asthma, and bronchial challenge testing guidelines (both international and country specific).
Please find below links to some examples of relevant guidelines/recommendations which include methacholine challenge testing;
Coates AL, Wanger J, Cockcroft DW, et al.
EurRespir J 2017; 49: 1601526 [https://doi.org/10.1183/13993003.01526-2016].
ATS Pulmonary Function Laboratory Management and Procedure Manual 3rd Edition (available for purchase)
Jack Wanger, Susan Blonshine, Catherine M Foss, et al.
Respir Care 2001;46(5):523–530
Crapo RO, Casaburi R, Coates AL, et al.
Am J RespirCrit Care Med 2000; 161: 309–329